Muscles and Nerves 189 



into an icy mass, the high temperature of the bird being 

 of itself insufhcient to obviate this, although assisted 

 by the great development of the subcutaneous fatty 

 layer, which far exceeds in thickness that of the corre- 

 sponding structure in the member of any other group 

 of birds, and recalls to mind the fatty deposit of 'blub- 

 ber' of the seals and cetaceans." 



When we looked at the blood of a bird, we saw the 

 tiny white corpuscles, which in life flow and move in 

 every direction, constanth' changing their outline; and 

 now if we take a piece of a bird's muscle or flesh and 

 examine it carefully, after ''teasing" it out into shreds 

 with a needle, we shall see another kind of cell-animal. 

 These are long and generally pointed, each a single cell 

 with a tin}' spot or nucleus in it, differing from the white- 

 blood animals in being able to stretch out and contract 

 in only one direction. When we will our arm to close 

 together, bringing our hand close to our shoulder, a thick 

 colony or bunch of these muscle-animals shortens, be- 

 comes stouter, and bulges uj) under the skin on our upper 

 arm. 



In our own bod}' the bones of the spinal column are 

 movable, and we can bend in almost every direction, 

 and so we are provided with many important back-muscles. 

 But if we have ever carved a chicken, we shall remem- 

 ber that the ribs and shoulder-bones are close to the sur- 

 face, and but poor pickings are to be had from them. 

 The breast and chest, on the contrary, are hidden in a 

 thick mass of muscles, most of which are concerned with 

 moving the wings in flight. The immense pectoral or 



